Gameplay is going to be split up into several modes.
Creative:
Build stuff. You can spawn blocks (any blocks) from thin air, and remove any block instantaneously.
No health, and you can’t die.
Play either single player or cooperatively.
(This is basically what the game is now)
Survival:
You need to gather resources to be able to use them. There’s a simple inventory, and a health bar. Blocky critters roam the land and want to hurt you. Eating food replenishes health.
Play either single player or cooperatively.
Team survival:
Same as survival, except you’re divided into two teams who try to kill each other
Fortress:
You and your friends build a fortress in creative or survival mode, then face off against another team’s fortress. Gameplay will probably be capture the flag.